A piezoelectric device has a piezoelectric effect that converts mechanical energy, such as vibrations or pressure, into electrical energy. For instance, when strain is applied to a piezoelectric device, electric power is generated according to the magnitude of the applied strain. Accordingly, a piezoelectric device may be used for, e.g. an electric generator. Further, a piezoelectric device has a reverse piezoelectric effect that converts electric energy into mechanical energy. For instance, when a voltage is applied to a piezoelectric device, the piezoelectric device deforms. Accordingly, a piezoelectric device may be used for, e.g. a sensor or an ink-jet head.
A conventional piezoelectric device includes a substrate, a lower electrode, a piezoelectric film, and an upper electrode. The lower electrode is formed on the substrate. The piezoelectric film is interposed between the lower electrode and the upper electrode. The piezoelectric film employs, for example, lead zirconate titanate (PZT). The lower electrode includes a conductive metal layer, a mixture layer, and a conductive oxide layer. The mixture layer contains conductive metal and conductive oxide. Thus, the mixture layer between the conductive metal layer and the conductive oxide layer prevents the conductive metal layer from being peeled off from the conductive oxide layer in the lower electrode.
A conventional piezoelectric device similar to the above piezoelectric device is disclosed in, e.g. Japanese Patent Laid-Open Publication No. 2007-300071.